Small electric motors have long used a helical or spiral groove on the shaft of the unit bearing motor acting as a viscosity pump to move oil through the unit bearing. This is disclosed in U.S. Pat. No. 2,522,985, which also disclosed use of a single groove in one end of the bearing post to receive a wick. The groove established an oil access hole from the exterior of the bearing post to the shaft aperture in which the shaft was journaled. The wick touched the rotating surface of the shaft so that the shaft could wipe some oil from the wick, and it was then slowly moved by the viscosity pump along the shaft into the bearing. Such lubrication systems were quite satisfactory for normal life motors with a horizontal shaft.
In recent years, greater emphasis has been placed on extremely long life motors, i.e., those which would run for 10 to 20 years without relubrication. For example, in refrigerator or freezer compartments, small air circulating fans were used in locations which made it extremely difficult to relubricate and the manufacturer could not rely upon the household user to relubricate the fan, yet the householder was extremely annoyed at having the motor fail, with the consequent high cost of field replacement.
Another problem was the lubrication of such motors with vertical shafts and how to supply a sufficient quantity and reliability of oil feed through the bearing.